Strap tensioning device for box nailing machines



Nov. 19, 1940. J. 0. TURNER 2,222,521

' STRAT" Q ENSIQNING DEVICE FOR BOX NAILING MACHINES Filed April 50, 1940 2 Sheets-Sheet 1' Zmnentor (Ittotnegs J, O. TURNER Nov. 19, 1940.

S'IRA P TENSIONING DEVICE FOR BOX NAILING MACHINES '2 Sheets-Sheet 2,

' Filed April 50, 1940 Patented Nov. 19, 1940 STRAP TENSIONING DEVICE FOR BOX NAILING MACHINES Joseph 0. Turner, Winston-Salem, N. 0., assignor to the Mengel Company, Louisville, Ky., a corporation of New Jersey Application April 30, 1940, Serial No. 332,611

8 Claims.

This invention relates to strap tensioning devices for use with box nailing machines of commercial form, for example, the Doig No. 4 nailing machine.

The tensioning device is so designed that it may take the place of the stop bar which limits the insertion of the end of the box under the row of nailing heads. This assures proper placing of the strap under the nailing heads, because the device itself becomes the positioning stop for the box.

The tensioner is operable by the driving bar of the nailer, which makes. a downward and return stroke for each nailing operation. Cam actuation of the. tensloner with excess travel against spring resisted lost motion, causes the tensioner to act in the initial part of the nailing stroke and before the nails are set, and still permits completion of the nailing stroke. Simple means are provided to adjust the timing and the tension developed.

The strap clamps are cam operated with powerful force multiplying effect in a closing direction, and with more rapid wedging action in the final opening shift to fully free the strap preparatory to turning the box for operation on the next face thereof. Thus, the tensioner does not impede manipulation of the strap.

The pull is in a straight line along the nailed surface of the box and tension is maintained until completion of the nailing stroke so that satisfactory operation is assured.

The device is simple and inexpensive to construct, and is readily adaptable to a considerable range of sizes and types of box nailing machines.

A preferred embodiment will now be described by reference to the accompanying drawings, in which:

Figure 1 is a face view of the attachment with portions of the guide housing broken away.

Fig. 2 is a plan View with the actuating slide in section. The position of the strap is indicated in dotted lines.

Fig. 3 is a section on the line 3-3 of Fig. 1.

Fig. 4 is a perspective view of the moving parts with the guide removed.

Fig. 5 is a fragmentary View of the front of a nailing machine with the attachment applied and arranged to serve as a stopbar.

The attachment is housed in a box-like rectangular hollow guide bar, generally indicated at ll in Fig. 5, and comprising a channeled bar Ma and a cover IIb (see Figs. 1 and 3) removably attached thereto.

In Fig. 5, the upright frame members of a nailing machine are indicated at I2, and four nailing heads are shown at I3, while the part I4 is the driving bar (or any equivalent part reciprocating down and back for each nailing operation). The guide bar II serves to limit the insertion of the end of a box under the row of nailing heads I3, and takes the place of the usual stop bar used in nailing machines for that purpose. ed by the use of brackets 15 with bolt slots I6 (see Fig. 3), through which the brackets I5 are bolted to frame members I2. Thus, the degree of insertion of the box may be chosen within reasonable limits.

In the device as illustrated, the strap is to be drawn to the right. Thus, to the right of the right hand nailing head I3 there is a slot I'I through which project the strap-clamping jaws H3 and I9. Beneath this there is a slot 2I in the bottom of the guide to accommodate the clamping yoke, and above it and in the cap Ila is a wider and longer slot 22, to accommodate the clamp-jaw actuator.

Mounted in the right hand end of the guide I I is a housing 23 with vertical guideway for the cam bar 24 and horizontal parallel guideways for the U-shaped pull yoke or actuator 25 and for the thrust bar 26.

The 'cam bar 24 has an inclined cam rib or feather 2T engaging a slot in thrust bar 26 and so arranged that descent of cam bar 24 forces thrust bar 25 to the right- The outer (right hand) end of thrust bar 26 carries a threaded extension 28 which passes freely through an opening in actuator 25. Stop nuts 29 limit relative movement of the extension 28 to the left relatively to actuator 25, and a coil compression spring 3i urges the actuator against the stop nuts. Nuts 32 on extension 28 serve as an adjustable spring seat.

Thus, a definite downward stroke of cam bar 24 is translated into a definite stroke of thrust bar 23 to the right, but if travel of actuator 25 is limited by tension developed in the strap,

spring 3| maintains and increases the tension but permits continued motion of thrust bar 26.

Cam bar 24 is driven by bar I4 through yoke 33. A clamping bolt 34 and slot 35 afford a 1ongitudinally adjustable connection permitting timing of commencement of the'tensioning action. Shims (not shown) may be inserted between members 24 and 33 to compensate for adjustment of bar II, if necessary.

The clamp jaws I8 and I9 are rigidfo-rward extensions on respective slides 36 and 31 housed in guide bar II. A-pin 38 in jaw I8 engages in a hole in jaw I9 to maintain alinement of the NEWS. at the leftward limit of motion of the slide to retain the slides and the jaws which they carry impositively in that position. A spring 42 actuates the detent and is adjustably stressed by screw 43. The slides and the jaws which they The guide bar II is adjustably mount- A detent 39 engages notch 4| in slide 31 respectively carry are actuated as a unit by means which will now be described.

A clamp yoke embraces the jaws I8 and I9 and comprises a top block 44 with two studs 45 which are fixed in the block and straddle the jaws, and a bottom block 46 loose on the studs. Nuts 41 on the studs (with check nuts as shown) adjust the blocks to limit the opening motion of the jaws. Thus the slides and jaws are constrained to move horizontallyasa unit. The upper jaw I9 has three pointed set screws 48 which are directed toward three holes 49 drilled in the jaw I8. Thus, adjustable clamping surfaces capable of deforming the strap (if desired) I are afforded. Obviously, the holes 49 need not go completely through the jaw I8, since countersinks would perform the intended function.

Pivoted at to top block 44 are two cam clamp levers 52 whose lower rounded cam ends bear on the top of jaw I9. The upper ends of levers 52are connected by offset link 53 to the separator'bars 54, pivotal connections being provided at both ends of link 53 as indicated at 53c and 53b. l

The separator bars 54 are hinged at 55 to actuator 25. They have a slender end 56 which lies between jaws I8 and I9 within guide bar H and a wedging cam portion 51 which forces the jaws apart as actuator 25 reaches its left-hand position. Thus the actuator 25 is connected through the link 53 and the cam levers 52 to the block 44. Block 44 is a part of the yoke which confines the jaws I8 and I9. ,Consequently, there is a driving connection from the actuator 25 to the two slides 35 and 31, which connection, however, permits such lost motion as is incident to the clamping motion of the levers 52.

Operation There areseveral different ways in which the box may be manipulated during the nailing and tensioning operation, depending somewhaton the form of the box. If the end of the box is square, the strap maybe attached by. a single handdri'ven nail near one corner, and then tensioned and nailed over each succeeding face of the box, which is turned counterclockwise 90 between successive nailing operations. In most cases, however, the end of the box is not square, and in such case the nailing operations are carried out on two different machines, to avoid adjustment of the supporting table. In' the latter case, a satisfactory practice is to nail the strap along one side of the box, without tensioning the strap. Then, the box is turned 180 and the strap is tensioned and nailed along the opposite side. machine, with a table differently adjusted, and the final nailing operations are performed on the top and bottom, one requiring a tensioning operation and the other not.

v The above are merely matters of manipulation, but they are mentioned to indicate the versatility of the device.

The tensioning device may be used with straps which are cut to length, and this is the preferred practice. However, the strap material may be drawn from a reel, so far as any limitations imposed by the tensiom'ng mechanism are concerned.

With the above understanding as to manipulation of the box, it will sufifice to describe one nailing and tensioning operation to bring out the functions of the mechanism above set forth.

Assume that the nailing machine is in it in- The box is then transferred to a second vice.

active position, that is, with the driving bar I4 in its upper limit of motion. Nails will have been supplied to the nailing head I3 and the machine is ready for its operative cycle.

The box indicated in dotted lines at A in Fig. 5, is supported under the nailing heads and against the guide bar II. The straps indicated at B is assumed to be connected to the box at the left side by a previous nailing operation of some sort, as above mentioned, and extends thence to the right between the jaws I8 and I9. Upon descent of the bar I4 and before the nails strike the strap, the motion of cam bar 24 will be sufficient to perform the following tensioning operation,

Motion of the thrust bar 26 to the right reacts through spring 3I to move the actuator 25 to the right. This carries the separator bars 54 far enough tothe right to permit the jaws I8 and I9 to close and immediately the jaws are freed, the cam levers 52 become effective as the result of clockwise rotation to force the jaw I9 downward against the jaw I8, so that the strap is tightly clamped between the jaws. Obviously, the clamping and releasing movements of the jaws I8 and I9 entail approach and separation of the slides 36 and 31.

During the initial movement, the impositive detent 39 holds the slide 31' in its leftmost position, but as soon as the clamping action is completed, the detent is overpowered. The effect is to cause the jaws I 8' and I9 to move to the right, while clamping the strap and the strap is drawn tightly across the edge of the box. As soon as the strap is tensioned, the nailing heads drive the nails. The spring 3I permits the necessary motion, while the actuator 25 is held by the strap.

On the return stroke, the cam levers 52 first release the jaws I8 and I9 and then the separator bars 54 cam the jaws apart. During this operation, the jaws move to the left until the slide 31 is again latched by the detent 39.

It will be observed that the strap is drawn smoothly across the face" of the box to be nailed,

that the housing of the mechanism supplants a stop forming a conventional part of ordinary nailing machines, that the tension is applied before the nails are driven and .is maintained after they are driven, and, finally, that the positive r separation of the jaws permits the strap to be fed readily between the jaws as the box is turned to expose its successive sides to the nailing head. While one embodiment of the invention which has demonstrated valuable characteristics in use has been illustrated, and While alterations are possible within the scope of the invention, it particularly should be understood that the device is susceptible of rearrangement and modification for use with nailing machines of different forms and types, the one illustrated being chosen merely because it is known in the art, and, hence, familiar to persons skilled in the art.

-A point that should be clearly understood is the actuating connection for the tensioning de- Most nailing machines have a driving bar which makes a double reciprocation, that is a forward and return stroke, for each nailing cycle, and it is commonly conveniently practicable to connect the cam bar 24 of the tensioning device through somesort of linkage to this driving bar. The commonest way of producing a double reciprocation of any member, such as the driving bar, is to connect it by a pitman and crank with a shaft which makes one rotation for each cycle of the machine, and so far as the operation of the cam bar 24 is concerned, it must be understood that any connection which will give this bar a double reciprocation, that is a forward and return stroke, for each nailing cycle of the machine, will suffice. The details of such connection fall within the ordinary skill of a mechanic.

Consequently, though a specific and probably the simplest arrangement; has been illustrated, this is intended solely for illustrative purposes and implies no unnecessary limitation.

What is claimed is:

1. A strap tensioning device for box nailing machines having a moving element which goes through a definite motion cycle as an incident to a nailing cycle of the machine, said device comprising a guide housing; a pair of slides longitudinally guided in said housing, each such slide including one of a pair of cooperating clamp jaws projecting from said housing and movable in the direction of the length of the housing; a reciprocable actuator movable in the direction of the length of said guide housing; a lost motion connection between said actuator and said jaws, said actuating connection including selectively acting means for closing said jaws when the actuator tends to shift the jaws in one direction, and for opening said jaws upon reversal of direction; and means for establishing a driving connection from the moving element of the nailing machine to said actuator, such that the motion cycle of the former produces a double reciprocation of the latter.

2. The combination defined in claim 1, in which the guide housing is dimensioned to extend across the nailing machine in position to serve as a stop for positioning the box to be nailed, whereby the guide itself serves to coordinate the position of the strap and of the nails to be driven.

3. A strap tensioning device for box nailing machines having a moving element which goes through a definite motion cycle as an incident to a nailing cycle of the machine, said device comprising a guide housing; a pair of slides longitudinally guided in said housing, each such-slide including one of a pair of cooperating clamp jaws projecting from said housing and movable in the direction of the length of the housing; a reciprocable actuator movable in the direction of the length of said guide housing; a lost motion connection between said actuator and said jaws, said actuating connection including selectively acting means for closing said jaws when the actuator tends to shift the jaws in one direction, and for opening said jaws upon reversal of direction; an impositive detent for resisting motion of said jaws from their open position; and means for establishing a driving connection from the moving element of the nailing machine tosaid actuator, such that the motion cycle of the former produces a double reciprocation of the latter.

4. The combination defined in claim 3, in which the impositive detent comprises a plunger, a spring urging said plunger in engaging direction, and means for adjusting the stress on the spring to vary the action of the detent.

5. A strap tensioning device for box nailing machines having a moving element which goes through a definite motion cycle as an incident to a nailing cycle of the machine, said device comprising a guide housing; a pair of slides longitudinally guided in said housing, each such slide including one of a pair of cooperating clamp jaws projecting from said housing and movable in the direction of the length of the housing; a reciprocable actuator movable in the direction of the length of said guide housing; a lost motion connection between said actuator and said jaws, said actuating connection including selectively acting means for closing said jaws when the actuator tends to shift the jaws in one direction, and for opening said jaws upon reversal of direction; and connecting means for establishing a driving connection from the moving element of the nailing machine to said actuator, such that the motion cycle of the former produces a double reciprocation of the latter, said connecting means including a yielding element adapted to permit excess travel of the driving element while the jaws are held undermaintained actuating stress.

6. A strap tensioning device for box nailing machines having a moving element which goes through a definite motion cycle as an incident to a nailing cycle of the machine, said device comprising a guide housing; a pair of slides longitudinally guided in said housing, each such slide including one of a pair of cooperating clamp jaws projecting from said housing and movable in the direction of the length of the housing; a reciprocable actuator movable in the direction of the length of said guide housing; a lost motion connection between said actuator and said jaws, said actuating connection including selectively acting means for closing said jaws when the actuator tends to shift the jaws in one direction,

and for opening said jaws upon reversal of direction; and connecting means for establishing a driving connection from the moving element of the nailing machine to said actuator, such that the motion cycle of the former produces a double reciprocation of the latter, said connecting means including a link adjustable to vary the timing of effective motion of the actuator with respect to motion of said driving element and a yielding connection to permit excess travel of the driving element with reference to said actuator.

'7. A strap tensioning device for box nailing machines of the type in which a driving element makes a forward and return stroke as an incident to each nailing cycle of the machine, said device comprising an elongated guide housing; a pair of slides longitudinally and transversely shiftable in said guide, each such slide carrying a corresponding one of a pair of coacting strapclamping jaws which project from said guide housing in position to clamp and tension a strap to be nailed; a yoke embracing a portion of said jaws; an actuator mounted to reciprocate in the direction of the length of said guide; a jaw closing clamp pivoted on said yoke and operatively connected to said actuator to force closed and to release said jaws upon forward and reverse shifts of said actuator respectively; wedging means associated with said actuator for forcing said jaws apart as a result of such reverse shift of the actuator; and means for establishing a driving connection between said driving element 

